There are several really good plugins, like "MultiSite Clone Duplicator", that allow you to clone/duplicate and existing site.
I run a multisite installation with over 200 sites. We started by creating a basic "template" site, which held all the basic/default settings we wanted for every new site. Then, we just clone that each time we want a new site.
1) No data/settings/options are lost, very rarely deleted, when deactivating plugins.
2) You do not need a wildcard subdomain unless you want to let visitors register for/create their own site/blog. But it doesn't hurt to have it. Else: explicitly add all subdomains in zone file.
3) In case you want several domains to map to the same site (special cases) ...
You should use the full URL of your site, as in https://www.example.com .
If you don't include the protocol (the "https://" part), then pages on your site (and links to other pages or media) won't work properly.